From: Robert Klemme <bob.news@...>
Date: 2004-07-14T20:42:26+09:00
Subject: Re: 'Initializing' modules

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"George Moschovitis" <gm@navel.gr> schrieb im Newsbeitrag
news:cd345h$sdg$1@ulysses.noc.ntua.gr...
> Hello everyone,
>
> I am looking for an elegant solution to a common problem.
> Lets say I have 2 modules (A, B):
>
> module A
> attr_accessor :val1
> attr_accessor :val2
>
> def initialize
> @val1 = @val2 = "A"
> end
> end
>
> module B
> attr_accessor :val3
> attr_accessor :val4
>
> def initialize
> @val3 = @val4 = "B"
> end
> end
>
> I include the modules in a news class:
>
> class MyClass
> include A, B
>
> def initialize
> # ???
> end
> end
>
> Is there a way to automatically call the initialization code for the two
> modules ? Is there a ruby idiom for this?
>
> Thanks in advance for any help!

The Ruby idiom is to use 'super' all over the place:

module A
  attr_accessor :val1
  attr_accessor :val2

  def initialize(*args)
    super
    @val1 = @val2 = "A"
  end
end

module B
  attr_accessor :val3
  attr_accessor :val4

  def initialize(*args)
    super
    @val3 = @val4 = "B"
  end
end

class MyClass
  include A, B

  def initialize
    super
    @foo = "bar"
  end
end

=>

irb(main):028:0> MyClass.new
=> #<MyClass:0x10187e08 @val3="B", @val2="A", @foo="bar", @val1="A",
@val4="B">

Note: to make this work seamless it's best to define initialize(*args) in
a module because otherwise there will be problems if you include a module
in different classes whose different base classes accept a different
amount of arguments.

You might want to experiment with the attached script a bit.

Regards

    robert


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#!/usr/bin/ruby=0A=
=0A=
class Base1=0A=
  def initialize=0A=
    super()=0A=
    @base1 =3D "base 1"=0A=
  end=0A=
end=0A=
=0A=
class Base2=0A=
  def initialize(v)=0A=
    super()=0A=
    @base2 =3D v=0A=
  end=0A=
end=0A=
=0A=
module Mod=0A=
  def initialize(*args)=0A=
    super=0A=
    @mod =3D "Mod"=0A=
  end=0A=
end=0A=
=0A=
class Der1 < Base1=0A=
  include Mod=0A=
=0A=
  def initialize=0A=
    super=0A=
    @der1 =3D "der 1"=0A=
  end=0A=
end=0A=
=0A=
class Der2 < Base2=0A=
  include Mod=0A=
=0A=
  def initialize(v)=0A=
    super=0A=
    @der2 =3D v=0A=
  end=0A=
end=0A=
=0A=
p Der1.ancestors=0A=
p Der2.ancestors=0A=
=0A=
begin=0A=
  puts "creating Der1"=0A=
  Der1.new=0A=
rescue Exception =3D> e=0A=
  p e=0A=
  puts e.backtrace=0A=
end=0A=
=0A=
begin=0A=
  puts "creating Der2"=0A=
  Der2.new "der 2"=0A=
rescue Exception =3D> e=0A=
  p e=0A=
  puts e.backtrace=0A=
end=0A=
=0A=
module Mod=0A=
  def initialize(*args)=0A=
    super()=0A=
    @mod =3D "Mod"=0A=
  end=0A=
end=0A=
=0A=
begin=0A=
  puts "creating Der1"=0A=
  Der1.new=0A=
rescue Exception =3D> e=0A=
  p e=0A=
  puts e.backtrace=0A=
end=0A=
=0A=
begin=0A=
  puts "creating Der2"=0A=
  Der2.new "der 2"=0A=
rescue Exception =3D> e=0A=
  p e=0A=
  puts e.backtrace=0A=
end=0A=

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